A negative electrode constituting a lithium secondary battery includes active material particles alloyed with lithium, such as silicon particles. The active material particles alloyed with lithium repeatedly expand and shrink following repeated occlusion and release of lithium ions caused by charging and discharging. A problem caused by the repeated expansion and shrinkage of the active material particles is that active material particles themselves and a binder contained in the active material layer are fractured and a charge-discharge cycle characteristic is deteriorated.
Accordingly, it has been suggested to use a polyimide resin as a binder contained in the active material layer, as shown in Patent Document 1.